Sometimes–not always—but sometimes they may convince themselves they’re mitigated, sometimes they fudge on what mitigated means. In a few cases, they just don’t care.
Again–read up on the Buffalo Creek Disaster. No one could have thought that that was a safe situation.
As I said–I am not saying this is true in this case. I am saying that criminal negligence happens in real life sometimes–not just in novels and movies.